/**
 * \addtogroup uip
 * @{
 */

/**
 * \defgroup slip Serial Line IP (SLIP) protocol
 * @{
 *
 * The SLIP protocol is a very simple way to transmit IP packets over
 * a serial line. It does not provide any framing or error control,
 * and is therefore not very widely used today.
 *
 * This SLIP implementation requires two functions for accessing the
 * serial device: slipdev_char_poll() and slipdev_char_put(). These
 * must be implemented specifically for the system on which the SLIP
 * protocol is to be run.
 */

/**
 * \file
 * SLIP protocol implementation
 * \author Adam Dunkels <adam@dunkels.com>
 */

/*
 * Copyright (c) 2001, Adam Dunkels.
 * All rights reserved. 
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.  
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
 *
 * This file is part of the uIP TCP/IP stack.
 *
 * $Id: slipdev.c,v 1.1.2.3 2003/10/07 13:23:01 adam Exp $
 *
 */

/*
 * This is a generic implementation of the SLIP protocol over an RS232
 * (serial) device. 
 *
 * Huge thanks to Ullrich von Bassewitz <uz@cc65.org> of cc65 fame for
 * and endless supply of bugfixes, insightsful comments and
 * suggestions, and improvements to this code!
 */

#include "uip.h"
#include "slipdev.h"
#include <string.h>

#define SLIP_END     0300
#define SLIP_ESC     0333
#define SLIP_ESC_END 0334
#define SLIP_ESC_ESC 0335

static u16_t len=0;
static u16_t tmplen = 0;
static u8_t lastc = 0;

/*-----------------------------------------------------------------------------------*/
/**
 * Send the packet in the uip_buf and uip_appdata buffers using the
 * SLIP protocol.
 *
 * The first 40 bytes of the packet (the IP and TCP headers) are read
 * from the uip_buf buffer, and the following bytes (the application
 * data) are read from the uip_appdata buffer.
 *
 */
/*-----------------------------------------------------------------------------------*/
#if 0 // this send 1 char at a time
void
slipdev_send(void)
{
  u16_t i;
  u8_t *ptr;
  u8_t c;

  slipdev_char_put(SLIP_END);

  ptr = uip_buf;
  for(i = 0; i < uip_len; ++i) {
    if(i == 40) {
      ptr = (char *)uip_appdata;
    }
    c = *ptr++;
    switch(c) {
    case SLIP_END:
      slipdev_char_put(SLIP_ESC);
      slipdev_char_put(SLIP_ESC_END);
      break;
    case SLIP_ESC:
      slipdev_char_put(SLIP_ESC);
      slipdev_char_put(SLIP_ESC_ESC);
      break;
    default:
      slipdev_char_put(c);
      break;
    }
  }
  slipdev_char_put(SLIP_END);
}
#else
#define SLIP_BUFFER_SIZE UIP_BUFSIZE + 64
void
slipdev_send(void)
{
  u16_t i;
  u8_t *ptr;
  u8_t c;
  static u8_t slip_tx_buf[SLIP_BUFFER_SIZE];
  u16_t buf_pos = 0;
  
  // Add starting SLIP_END
  slip_tx_buf[buf_pos++] = SLIP_END;

  ptr = uip_buf;
  for(i = 0; i < uip_len; ++i) {
    if(i == 40) {
      ptr = (u8_t *)uip_appdata;
    }
    c = *ptr++;
    
    // Check if we need space for worst case (2 bytes for escaped char)
    if (buf_pos >= SLIP_BUFFER_SIZE - 2) {
      slipdev_write(slip_tx_buf, buf_pos);
      buf_pos = 0;
    }
    
    switch(c) {
    case SLIP_END:
      slip_tx_buf[buf_pos++] = SLIP_ESC;
      slip_tx_buf[buf_pos++] = SLIP_ESC_END;
      break;
    case SLIP_ESC:
      slip_tx_buf[buf_pos++] = SLIP_ESC;
      slip_tx_buf[buf_pos++] = SLIP_ESC_ESC;
      break;
    default:
      slip_tx_buf[buf_pos++] = c;
      break;
    }
  }
  
  // Add ending SLIP_END
  if (buf_pos >= SLIP_BUFFER_SIZE) {
    slipdev_write(slip_tx_buf, buf_pos);
    buf_pos = 0;
  }
  slip_tx_buf[buf_pos++] = SLIP_END;
  
  // Send remaining bytes
  slipdev_write(slip_tx_buf, buf_pos);
}
#endif
/*-----------------------------------------------------------------------------------*/
/** 
 * Poll the SLIP device for an available packet.
 *
 * This function will poll the SLIP device to see if a packet is
 * available. It uses a buffer in which all avaliable bytes from the
 * RS232 interface are read into. When a full packet has been read
 * into the buffer, the packet is copied into the uip_buf buffer and
 * the length of the packet is returned.
 *
 * \return The length of the packet placed in the uip_buf buffer, or
 * zero if no packet is available.
 */
/*-----------------------------------------------------------------------------------*/
u16_t
slipdev_poll(void)
{
  u8_t c;
  static u8_t slip_buf[UIP_BUFSIZE];
  
  while(slipdev_char_poll(&c)) {
     switch(c) {
        case SLIP_ESC:
           lastc = c;
           break;

        case SLIP_END:
           lastc = c;
           /* End marker found, we copy our input buffer to the uip_buf
              buffer and return the size of the packet we copied. */
           memcpy(uip_buf, slip_buf, len);
           tmplen = len;
           len = 0;
           return tmplen;

        default:     
           if(lastc == SLIP_ESC) {
              lastc = c;
              /* Previous read byte was an escape byte, so this byte will be
                 interpreted differently from others. */
              switch(c) {
                 case SLIP_ESC_END:
                    c = SLIP_END;
                    break;
                 case SLIP_ESC_ESC:
                    c = SLIP_ESC;
                    break;
              }
           } else {
              lastc = c;
           }

           slip_buf[len] = c;
           ++len;

           if(len > UIP_BUFSIZE) {
              len = 0;
           }
           break;
     }
  }
  return 0;
}
/*-----------------------------------------------------------------------------------*/
/**
 * Initialize the SLIP module.
 *
 * This function does not initialize the underlying RS232 device, but
 * only the SLIP part.
 */ 
/*-----------------------------------------------------------------------------------*/
void
slipdev_init(void)
{
  lastc = len = 0;
}
/*-----------------------------------------------------------------------------------*/

/** @} */
/** @} */
